Anode materials, their preparation methods, and batteries

Abstract

This application provides an anode material, its preparation method, and a battery. The anode material includes hard carbon and a coating layer disposed on the surface of the hard carbon, wherein the coating layer includes soft carbon. The total pore volume of the anode material, measured by carbon dioxide adsorption-desorption, has a pore size of 0.3 nm-1 nm and is greater than 0.03 cm³. 3 / g; the ratio of the ultramicropore volume V1 to the submicropore volume V2 of the negative electrode material, V1 / V2 ≥ 20; the ultramicropore volume V1 is the pore volume with a pore size of 0.3nm-0.7nm measured by carbon dioxide adsorption-desorption; the submicropore volume V2 is the pore volume with a pore size of 1nm-2nm measured by nitrogen adsorption-desorption; the specific surface area S2 of the negative electrode material measured by nitrogen adsorption-desorption is less than 10m². 2 / g. This anode material comprises a hard carbon core and a soft carbon coating layer, exhibiting high total pore volume, high proportion of micropores, and low specific surface area, thus achieving a balance between high capacity, high initial coulombic efficiency, and high compaction density.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a negative electrode material, its preparation method, and a battery. Background Technology

[0002] Amorphous carbon materials, due to their large interlayer spacing and relatively disordered microstructure arrangement, are currently a promising anode material for sodium-ion batteries. With the iterative development of sodium-ion batteries, the industry has placed higher demands on the energy density of amorphous carbon materials, thus urgently requiring effective methods to improve their capacity. It is generally believed that the sodium storage mechanism of amorphous carbon materials includes three stages: adsorption, intercalation, and pore filling. Among these, pore-filling sodium storage has a lower potential and can provide higher energy density. Activating pore formation to improve pore-filling capacity is one of the commonly used methods in the industry. However, the actual capacity improvement of amorphous carbon materials obtained through activation pore formation is not significant at present, presenting a contradiction between "increasing capacity" and "losing compaction density," making it difficult to simultaneously achieve high capacity, high initial coulombic efficiency, and high compaction density. Summary of the Invention

[0003] In view of this, embodiments of this application provide an anode material, a method for preparing the same, and a battery. The anode material includes a hard carbon core and a soft carbon coating layer, and has a high total pore volume, a high proportion of micropores, and a low specific surface area. The anode material can simultaneously possess high capacity, high initial coulombic efficiency, and high compaction density.

[0004] In a first aspect, embodiments of this application provide a negative electrode material, the negative electrode material comprising hard carbon and a coating layer disposed on the surface of the hard carbon, the coating layer comprising soft carbon;

[0005] The total pore volume V of the negative electrode material, measured by carbon dioxide adsorption-desorption, has a pore size of 0.3 nm-1 nm. 总1 Greater than 0.03cm 3 / g; the ratio of the ultramicropore volume V1 to the submicropore volume V2 of the negative electrode material is V1 / V2≥20; wherein, the ultramicropore volume V1 is the pore volume with a pore size of 0.3nm-0.7nm measured by carbon dioxide adsorption-desorption; the submicropore volume V2 is the pore volume with a pore size of 1nm-2nm measured by nitrogen adsorption-desorption;

[0006] The specific surface area S2 of the negative electrode material, measured by nitrogen adsorption-desorption, is less than 10 m². 2 / g.

[0007] The negative electrode material provided in this application embodiment is a porous material with a high total pore volume V. 总1With a high proportion of micropores and a low specific surface area, and comprising both a hard carbon core and a soft carbon coating layer, the anode material can simultaneously possess high capacity, high initial coulombic efficiency, and high compaction density; among these, the anode material exhibits a high total pore volume V measured by carbon dioxide adsorption-desorption. 总1 The anode material can provide a relatively large number of active sites for filling pores and storing sodium, which is beneficial to improving capacity. At the same time, the anode material has a high V1 / V2 ratio, that is, a high proportion of micropores, which can improve the effective sodium storage utilization of the pores and better maintain a high compaction density while improving capacity. The anode material has a high proportion of micropores and a relatively low specific surface area S2 measured by nitrogen adsorption-desorption, which helps to reduce the occurrence of side reactions of solvent molecules and solvated ions in the pores and on the surface of the anode material, thereby reducing the consumption of additional active sodium and improving the first coulombic efficiency. The coating layer containing soft carbon can fill the relatively large openings on the surface of hard carbon, reduce the specific surface area of ​​the anode material, and thus improve capacity, compaction density and first coulombic efficiency.

[0008] In this embodiment of the application, the specific surface area S2 of the negative electrode material, measured by nitrogen adsorption-desorption, is less than 5 m². 2 / g. The anode material has a relatively lower specific surface area S2, which is beneficial for further improving the first coulombic efficiency.

[0009] In this embodiment, the pore size distribution diagram of the negative electrode material, obtained based on carbon dioxide adsorption-desorption characterization, shows four peaks in the pore size range of 0.3 nm to 1 nm, corresponding to pore size ranges of 0.3 nm to 0.39 nm, 0.39 nm to 0.5 nm, 0.5 nm to 0.7 nm, and 0.7 nm to 1.0 nm, respectively. The abundant and hierarchically distributed micropores within the negative electrode material are beneficial for improving its kinetic performance.

[0010] In this embodiment of the application, the total pore volume V of the negative electrode material, measured by carbon dioxide adsorption-desorption, has a pore size of 0.3 nm-1 nm. 总1 Greater than 0.03cm 3 / g and less than 0.3cm 3 / g; The total pore volume V of the negative electrode material, measured by nitrogen adsorption-desorption, with a pore size of 1nm-50nm. 总2 Less than or equal to 0.02cm 3 / g. The negative electrode material has a higher total pore volume V. 总1 This is beneficial for improving capacity. The anode material has a relatively low Vg. 总2 It can minimize the pore space that cannot be effectively used for sodium storage, thereby improving both capacity and compaction density.

[0011] In this embodiment of the application, the pore volume V1 of the ultramicropore is greater than 0.02 cm.3 / g. A larger micropore volume means more micropores. This is achieved by controlling the micropore volume V1 to >0.02cm². 3 / g can improve the utilization rate of sodium storage in porous structures and increase energy density.

[0012] In this embodiment of the application, the submicropore volume V2 is less than 0.0025 cm³. 3 / g. The smaller the submicropore volume V2, the fewer pores with a diameter of 1nm-2nm can be measured by nitrogen adsorption-desorption, which helps to reduce the adverse effect of submicropores on improving pore space utilization.

[0013] In this embodiment of the application, the specific surface area S1 of the negative electrode material, measured by carbon dioxide adsorption-desorption, is greater than 100 m². 2 / g. The specific surface area measured by carbon dioxide adsorption-desorption is primarily the ultraporous surface area. The specific surface area S1 measured by carbon dioxide adsorption-desorption should be controlled to be greater than 100 m². 2 / g helps to provide more sodium deposition sites and improve the capacity of the anode material.

[0014] In this embodiment, the ratio of the specific surface area S1 measured by carbon dioxide adsorption-desorption to the specific surface area S2 measured by nitrogen adsorption-desorption, S1 / S2, is greater than 30. This allows for more sodium deposition sites provided by the micropores, which is beneficial for improving the capacity of the negative electrode material.

[0015] In this embodiment, the full width at half maximum (FWHM) of the XRD diffraction peak of the (002) crystal plane of the negative electrode material is less than 7.0°. A narrower FWHM for the (002) peak in the negative electrode material results in a larger crystal domain size, which is beneficial for increasing the compaction density of the negative electrode material.

[0016] In this embodiment, the full width at half maximum (FWHM) of the XRD diffraction peak of the (100) crystal plane of the negative electrode material is less than 3.5°. A narrower FWHM for the (100) peak results in a larger crystal domain size, which is beneficial for increasing the compaction density of the negative electrode material.

[0017] In this embodiment, the thickness of the coating layer is 1 nm to 10 nm. A thinner coating layer facilitates ion diffusion and transport, thereby improving the kinetic performance of the anode material.

[0018] In this embodiment, the intensity ratio of the D peak to the G peak in the Raman spectrum of the negative electrode material is ID / IG ≥ 1.10. A larger ID / IG ratio indicates that there are more defects in the coating layer, which can increase the wettability of the negative electrode material in the electrolyte and improve the kinetic performance of the negative electrode material.

[0019] In this embodiment of the application, the intensity ratio of the D peak to the G peak in the Raman spectrum of the negative electrode material, ID / IG, is: 1.12 ≤ ID / IG ≤ 1.3. A suitable ID / IG ratio allows the negative electrode material to achieve increased wettability while avoiding an increase in side reactions caused by excessive defects.

[0020] In this embodiment, the carbon interlayer spacing of the negative electrode material is 0.370 nm ≤ d002 ≤ 0.380 nm. A larger interlayer spacing in the negative electrode material facilitates ion insertion and extraction, and improves the kinetic performance of the negative electrode material.

[0021] In this embodiment of the application, the powder compaction density of the negative electrode material is greater than 1.03 g / cm³. 3 The reversible specific capacity of the negative electrode material is greater than 340 mAh / g; the initial coulombic efficiency of the negative electrode material is greater than or equal to 88%. The negative electrode material has a large compaction density, which is beneficial for achieving high battery capacity; the negative electrode material has a large reversible specific capacity, so the battery can store and release more energy during charging and discharging, thereby improving the battery's energy density; the negative electrode material has a high initial coulombic efficiency, resulting in lower initial losses, which is beneficial for improving the overall performance and range of the battery.

[0022] The second aspect of this application provides a method for preparing a negative electrode material, including:

[0023] The first carbon source is pretreated by heating to obtain the pretreated product;

[0024] The pretreated product was mixed with a zinc-containing catalyst and then activated in a nitrogen atmosphere for the first stage, followed by a carbon dioxide atmosphere for the second stage, to obtain the activated product.

[0025] The activated product is subjected to a first carbonization treatment to obtain hard carbon.

[0026] The hard carbon is mixed with a second carbon source and then subjected to a second carbonization treatment to form a coating layer on the surface of the hard carbon, thereby obtaining a negative electrode material.

[0027] The method for preparing the negative electrode material provided in this application, through a special physicochemical activation process and liquid phase coating process, enables the product to have a higher ultra-micropore volume and proportion, improves the utilization rate of the pore structure for sodium storage, and thus obtains a higher sodium storage capacity and a relatively higher compaction density; at the same time, it can also make the negative electrode material have a smaller (002) peak and (100) peak half width at half maximum, further improving the compaction density and increasing the capacity.

[0028] In this embodiment, the zinc-containing catalyst comprises one or more of zinc salts and zinc oxides. The zinc salt can be zinc acetate, zinc carbonate, zinc oxalate, etc., and the zinc oxide can be zinc oxide (ZnO). The zinc-containing catalyst can induce the directional activation of the pretreated product by carbon dioxide, thereby achieving the formation of abundant ultrapores. The directional activation can be achieved by CO2 etching the pretreated product to form micropores under the catalysis of the zinc-containing catalyst; the activation reaction of CO2 occurs directionally towards the interior of the pretreated product as the zinc-containing catalyst is distributed.

[0029] In this embodiment, the nitrogen flow rate for the first stage of activation is 0.1 L / min to 0.5 L / min; the carbon dioxide flow rate for the second stage of activation is 0.1 L / min to 2 L / min. A suitable nitrogen flow rate promotes more uniform pre-activation. Appropriate carbon dioxide flow rate control facilitates the activation of the pretreated product using carbon dioxide, ensuring activation efficiency while avoiding excessively rapid reaction and pore size expansion, ultimately leading to the formation of a narrow pore structure.

[0030] In this embodiment, the activation temperature of the first stage is 200℃-300℃; the activation temperature of the second stage is 800℃-950℃. After mixing the pretreated product with the zinc-containing catalyst, it is first treated at a suitable lower temperature under a nitrogen atmosphere. This softens the first carbon source and allows the zinc-containing catalyst to fully penetrate and disperse into the first carbon source bulk phase, completing the pre-activation. Controlling the second stage activation at a relatively higher suitable temperature allows the zinc-containing catalyst to better induce carbon dioxide to activate the pretreated product, controlling the reaction rate to form more micropores.

[0031] In this embodiment, the heating rate of the first activation stage is 1℃ / min-10℃ / min, and the holding time is 1-2 hours; the heating rate of the second activation stage is 1℃ / min-10℃ / min, and the holding time is 2-6 hours. A suitable first activation heating rate promotes more uniform pre-activation, and a suitable holding time ensures more complete pre-activation. A suitable second activation heating rate promotes more uniform activation, and a suitable holding time allows for better control of the activation degree and pore size distribution.

[0032] In this embodiment, the heating pretreatment is carried out in a nitrogen atmosphere at a temperature of 200℃-600℃. A suitable heating pretreatment temperature allows the small molecules and heteroatom groups of the first carbon source to slowly decompose and overflow, avoiding the formation of macropores. Simultaneously, after the heteroatoms overflow, the carbon structure crosslinks and rearranges to form a bridging network structure, ultimately resulting in more micropores.

[0033] In this embodiment, the first carbon source includes one or more of asphalt, resin, and biomass. The aforementioned first carbon source raw materials are readily available and are advantageous for obtaining anode materials with relatively higher compaction densities.

[0034] In this embodiment of the application, the first carbon source includes one or more of asphalt and resin. The operation of pre-treating the first carbon source by heating is as follows: the first carbon source is mixed with a crosslinking agent and then subjected to heat pre-treatment. Introducing a crosslinking agent during the heat pre-treatment process can enable the first carbon source to form a pre-crosslinked oxidation product, whose crosslinking sites can provide pore-forming sites, which is beneficial for the subsequent formation of narrow pores with more uniform size and distribution.

[0035] In this embodiment, the crosslinking agent includes anhydride crosslinking agents, specifically one or more of 1,2,4-phenyltriglyceridyl anhydride, maleic anhydride, and maleic anhydride. These crosslinking agents have relatively small molecular weights, which is beneficial for forming narrow ultrapores in the subsequent negative electrode material.

[0036] In this embodiment, the second carbon source comprises a carbon source material with a softening point of less than 200°C. The lower softening point of the second carbon source is advantageous for preparing a thin and uniform coating layer structure via a liquid-phase coating process.

[0037] In this embodiment, the temperature of the first carbonization treatment is 1200℃-1400℃; the temperature of the second carbonization treatment is 900℃-1200℃. A suitable first carbonization temperature allows for further uniform cross-linking of the activated product, stabilizing the structure and ensuring complete carbonization; it also allows the resulting hard carbon to retain more ion diffusion channels, improving kinetic performance. A suitable second carbonization temperature is beneficial for forming a complete and thin high-quality coating layer.

[0038] A third aspect of this application provides a composite negative electrode material, which includes the negative electrode material described in the first aspect of this application or the negative electrode material prepared by the preparation method described in the second aspect of this application, as well as a second negative electrode active material different from the negative electrode material.

[0039] A fourth aspect of this application provides a negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a negative electrode active layer disposed on the negative electrode current collector, the negative electrode active layer comprising the negative electrode material described in the first aspect of this application; or comprising the negative electrode material prepared by the preparation method described in the second aspect of this application; or comprising the composite negative electrode material described in the third aspect of this application.

[0040] A fifth aspect of this application provides a battery comprising a positive electrode, a negative electrode, and an electrolyte disposed between the positive and negative electrode, wherein the negative electrode comprises the negative electrode described in the fourth aspect of this application. Using a negative electrode material that combines high capacity, high initial coulombic efficiency, and high compaction density can improve battery performance.

[0041] This application also provides an electrical device, which includes a power module and the battery described in the fifth aspect of this application, wherein the battery supplies power to the power module. The battery uses a negative electrode material that combines high capacity, high initial coulombic efficiency, and high compaction density, which can improve the performance of the electrical device and enhance product competitiveness.

[0042] This application also provides an energy storage device, which includes a battery module. The battery module includes a battery mounting portion and the battery described in the fifth aspect, and the battery is mounted on the battery mounting portion. The battery uses a negative electrode material that combines high capacity, high initial coulombic efficiency, and high compaction density, which can improve the performance of the energy storage device and enhance product competitiveness. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the structure of the negative electrode material 100 provided in the embodiments of this application;

[0044] Figure 2 This is a schematic diagram of the cross-sectional structure of the negative electrode 20 provided in the embodiments of this application;

[0045] Figure 3 This is a schematic diagram of the structure of the sodium-ion battery 300 provided in the embodiments of this application;

[0046] Figure 4 This is a schematic diagram of the structure of the electrical equipment 400 provided in the embodiments of this application;

[0047] Figure 5 This is an HRTEM (High Resolution Transmission Electron Microscope) image of the negative electrode material prepared in Example 1 of this application;

[0048] Figure 6 This is the XRD (X-ray diffraction) spectrum of the negative electrode material prepared in Example 1 of this application. Detailed Implementation

[0049] The embodiments of this application will now be described in conjunction with the accompanying drawings.

[0050] Compared to lithium-ion batteries, sodium ions have an atomic radius at least 35% larger than lithium ions, making them more difficult to insert and extract into materials. Limited by interlayer spacing, the industry believes that graphite-based materials, the mainstream material used in lithium-ion batteries, are unsuitable as anode materials for sodium-ion batteries. Amorphous carbon materials, due to their larger interlayer spacing and relatively disordered microstructure, are currently a promising anode material for sodium-ion batteries. However, with the continuous development and iteration of sodium-ion batteries, the industry has placed higher demands on the energy density of amorphous carbon materials, thus urgently requiring effective methods to improve their capacity. It is generally believed that the sodium storage mechanism of amorphous carbon materials includes three stages: adsorption, intercalation, and pore filling. Among these, pore-filling sodium storage has a lower potential and can provide higher energy density. Therefore, activating pore formation to improve pore-filling capacity has become a common method for improving the capacity of amorphous carbon materials. However, currently, amorphous carbon materials obtained through activation pore formation present a contradiction between "increasing capacity" and "losing compaction density," resulting in insignificant actual capacity improvement and difficulty in simultaneously achieving high capacity, high initial coulombic efficiency, and high compaction density. In view of this, embodiments of this application provide a negative electrode material comprising a hard carbon core and a soft carbon coating layer, having a high total pore volume, a high proportion of micropores, and a low specific surface area. This negative electrode material can simultaneously possess high capacity, high initial coulombic efficiency, and high compaction density.

[0051] See Figure 1 , Figure 1 This is a schematic diagram of the structure of the negative electrode material 100 provided in the embodiment of this application. The negative electrode material 100 in the embodiment of this application includes hard carbon 101 and a coating layer 102 disposed on the surface of hard carbon 101. The coating layer 102 includes soft carbon.

[0052] The total pore volume V of the negative electrode material 100 with a pore size of 0.3 nm-1 nm, measured by carbon dioxide adsorption-desorption. 总1 Greater than 0.03cm 3 / g; The ratio of the ultramicropore volume V1 to the submicropore volume V2 of the negative electrode material 100 is V1 / V2≥20; wherein, the ultramicropore volume V1 is the pore volume with a pore size of 0.3nm-0.7nm measured by carbon dioxide adsorption-desorption; the submicropore volume V2 is the pore volume with a pore size of 1nm-2nm measured by nitrogen adsorption-desorption;

[0053] The specific surface area S2 of the negative electrode material 100, measured by nitrogen adsorption-desorption, is less than 10 m². 2 / g.

[0054] The negative electrode material 100 provided in this embodiment is a porous material with a high total pore volume V. 总1With a high proportion of micropores and a low specific surface area, and comprising both a hard carbon core and a soft carbon coating layer, the anode material 100 can simultaneously possess high capacity, high initial coulombic efficiency, and high compaction density; among these, the anode material 100 has a high total pore volume V measured by carbon dioxide adsorption-desorption. 总1 The anode material 100 can provide a relatively large number of active sites for sodium storage, which is beneficial to improving capacity. At the same time, the anode material 100 has a high V1 / V2 ratio, that is, a high proportion of micropores, which can improve the effective sodium storage utilization of the pores and better maintain a high compaction density while improving capacity. The anode material 100 has a high proportion of micropores and a relatively low specific surface area S2 measured by nitrogen adsorption-desorption, which helps to reduce the occurrence of side reactions of solvent molecules and solvated ions in the pores and on the surface of the anode material, thereby reducing the consumption of additional active sodium and improving the first coulombic efficiency. The soft carbon coating layer can fill the relatively large openings on the surface of hard carbon, reduce the specific surface area of ​​the anode material 100, and thus improve capacity, compaction density and first coulombic efficiency.

[0055] The test methods for carbon dioxide adsorption-desorption and nitrogen adsorption-desorption are as follows:

[0056] Carbon dioxide adsorption-desorption test: A certain amount of sample was weighed into a sample tube and degassed under vacuum at 300℃ for 4 hours. Then, in a 0℃ ice-water environment, the sample was tested using a specific surface area and pore size analyzer (ASAP 2460). After the test, the pore structure was analyzed using the HS-2D-NLDFT, Carbon, CO2, 273 analytical model to obtain the total pore volume V. 总1 , Micropore volume V1, Specific surface area S1.

[0057] Nitrogen adsorption-desorption test: A certain amount of sample was weighed into a sample tube and degassed under vacuum at 300℃ for 4 hours. Then, under liquid nitrogen environment, the surface area and pore size were tested using a specific surface area and pore size analyzer (ASAP 2460). After the test, the pore structure was analyzed using the HS-2D-NLDFT, Carbon, N2, 77 analytical model to obtain the total pore volume V. 总2 , Submicropore volume V2, Specific surface area S2.

[0058] Total pore volume refers to the total volume (i.e., total volume) of all pores per unit mass of a porous solid. The total pore volume V, measured by carbon dioxide adsorption-desorption, is for pore sizes ranging from 0.3 nm to 1 nm. 总1 This refers to the total pore volume of pores with a diameter of 0.3 nm to 1 nm, as measured by carbon dioxide adsorption-desorption testing. The total pore volume V of pores with a diameter of 1 nm to 50 nm, as measured by nitrogen adsorption-desorption testing. 总2This refers to the total volume of pores with a pore size of 1nm-50nm, measured by nitrogen adsorption-desorption testing. The ultramicropore volume V1 is the total volume of pores with a pore size of 0.3nm-0.7nm, measured by carbon dioxide adsorption-desorption. The submicropore volume V2 is the total volume of pores with a pore size of 1nm-2nm, measured by nitrogen adsorption-desorption.

[0059] In this embodiment, the ratio of the micropore volume V1 to the submicropore volume V2 of the negative electrode material 100, V1 / V2, is ≥20. Sodium ions stored by the pore-filling mechanism may deposit on the inner wall of the pores, failing to completely fill the pore space. This results in some pore space not being effectively utilized. By controlling the ratio of micropores V1 / V2 to a larger value, this application can have a relatively larger number of smaller micropores, thereby maximizing the space utilization of the pores, increasing the capacity of the negative electrode material 100, and avoiding a significant decrease in compaction density. In some embodiments of this application, the ratio of the micropore volume V1 to the submicropore volume V2 of the negative electrode material 100, V1 / V2, is ≥30. In some embodiments of this application, the ratio of the micropore volume V1 to the submicropore volume V2 of the negative electrode material 100, V1 / V2, is ≥40. In some embodiments of this application, the ratio V1 / V2 of the ultramicropore volume V1 to the submicropore volume V2 of the negative electrode material 100 is ≥50. In some embodiments of this application, the ratio V1 / V2 of the ultramicropore volume V1 to the submicropore volume V2 of the negative electrode material 100 is ≥60. Exemplarily, the ratio V1 / V2 of the ultramicropore volume V1 to the submicropore volume V2 of the negative electrode material 100 is 20, 30, 40, 50, 60, 70, 80, 90, 100, or 110.

[0060] In this embodiment, the total pore volume V of the negative electrode material 100, with a pore size of 0.3 nm-1 nm, is measured by carbon dioxide adsorption-desorption. 总1 Greater than 0.03cm 3 / g. The negative electrode material 100 has a high density greater than 0.03 cm⁻¹. 3 / g total pore volume V 总1 It can provide a relatively large number of active sites for filling pores and storing sodium, which is beneficial to improving capacity. In some embodiments of this application, the total pore volume V of the negative electrode material 100 with a pore size of 0.3 nm-1 nm, as measured by carbon dioxide adsorption-desorption, is... 总1 Greater than 0.04cm 3 / g. In some embodiments of this application, the total pore volume V of the negative electrode material 100, with a pore size of 0.3nm-1nm, is measured by carbon dioxide adsorption-desorption. 总1 Greater than 0.09cm 3 / g. In some embodiments of this application, the total pore volume of the negative electrode material with a pore size of 0.3nm-1nm, as measured by carbon dioxide adsorption-desorption, is greater than 0.03cm³. 3 / g and less than 0.3cm 3 / g. Anode material 100 has a higher total pore volume V. 总1 This is beneficial for improving capacity. For example, the total pore volume V of the negative electrode material 100, measured by carbon dioxide adsorption-desorption, has a pore size of 0.3 nm-1 nm. 总1 It can be 0.03cm 3 / g, 0.04cm 3 / g, 0.05cm 3 / g, 0.08cm 3 / g, 0.10cm 3 / g, 0.12cm 3 / g, 0.14cm 3 / g, 0.16cm 3 / g, 0.18cm 3 / g.

[0061] In this embodiment, the specific surface area S2 of the negative electrode material 100, measured by nitrogen adsorption-desorption, is less than 10 m². 2 / g. The negative electrode material 100 has a relatively low molecular weight (less than 10m). 2 A specific surface area S2 of / g is beneficial for reducing side reactions of solvent molecules and solvated ions on the surface of the negative electrode material, thereby reducing the consumption of additional active sodium and improving the initial coulombic efficiency. In some embodiments of this application, the specific surface area S2 of the negative electrode material 100, measured by nitrogen adsorption-desorption, is less than 5m². 2 / g. In some embodiments of this application, the specific surface area S2 of the negative electrode material 100, measured by nitrogen adsorption-desorption, is less than 4m². 2 / g. The negative electrode material 100 has a relatively low specific surface area S2, which is beneficial for further improving the first coulombic efficiency. For example, the specific surface area S2 of the negative electrode material 100, measured by nitrogen adsorption-desorption, is 9m². 2 / g、8m 2 / g、9m 2 / g、6m 2 / g、5m 2 / g、4m 2 / g、3m 2 / g.

[0062] In this embodiment, the pore size distribution diagram of the negative electrode material 100, based on carbon dioxide adsorption-desorption characterization, shows four peaks in the pore size range of 0.3 nm to 1 nm, corresponding to pore size ranges of 0.3 nm to 0.39 nm, 0.39 nm to 0.5 nm, 0.5 nm to 0.7 nm, and 0.7 nm to 1.0 nm, respectively. The negative electrode material 100 has abundant and hierarchically distributed micropores, which is beneficial for improving its kinetic performance.

[0063] In this embodiment of the application, the total pore volume V of the negative electrode material 100, measured by nitrogen adsorption-desorption, has a pore size of 1nm-50nm. 总2 Less than or equal to 0.02cm 3 / g. Total pore volume V measured by nitrogen adsorption-desorption. 总2 The smaller the diameter, the smaller the total volume of pores larger than the ultramicropore diameter. The total pore volume V, measured by nitrogen adsorption-desorption, is for pores with diameters ranging from 1 nm to 50 nm. 总2 Controlled to less than or equal to 0.02cm 3 / g, which minimizes the pore space that cannot be effectively used for sodium storage, thereby improving both capacity and compaction density. In some embodiments of this application, the total pore volume V of the negative electrode material 100, measured by nitrogen adsorption-desorption, has a pore size of 1nm-50nm. 总2 Less than 0.011cm 3 / g. For example, the total pore volume V of the negative electrode material 100, with a pore size of 1nm-50nm, measured by nitrogen adsorption-desorption. 总2 It is 0.02cm 3 / g, 0.018cm 3 / g, 0.015cm 3 / g, 0.014cm 3 / g, 0.012cm 3 / g, 0.010cm 3 / g, 0.008cm 3 / g, 0.005cm 3 / g, 0.003cm 3 / g.

[0064] In this embodiment of the application, the pore volume V1 of the ultramicropores is greater than 0.02 cm. 3 / g. A larger micropore volume means more micropores. This application controls the micropore volume V1 to >0.02cm². 3 / g can improve the sodium storage utilization rate of the porous structure and increase the energy density. In some embodiments of this application, the pore volume V1 of the ultramicropores is ≥0.05cm³. 3 / g. In some embodiments of this application, the pore volume V1 of the ultramicropores is ≥0.1cm³. 3 / g. For example, the pore volume V1 of the ultramicropores is 0.021 cm³. 3 / g, 0.023cm 3 / g, 0.025cm 3 / g, 0.040cm 3 / g, 0.060cm 3 / g, 0.080cm 3 / g, 0.10cm 3 / g, 0.12cm 3 / g.

[0065] In this embodiment of the application, the submicropore volume V2 is less than 0.0025 cm³. 3 / g. The smaller the submicropore volume V2, the fewer pores with a diameter of 1nm-2nm measured by nitrogen adsorption-desorption, which helps to reduce the adverse effect of submicropores on improving pore space utilization. In some embodiments of this application, the submicropore volume V2 ≤ 0.0021cm³. 3 / g. In some embodiments of this application, the submicropore volume V2 ≤ 0.0015 cm³. 3 / g. For example, the submicropore volume V2 is 0.0024 cm³. 3 / g, 0.0022cm 3 / g, 0.0020cm 3 / g, 0.0019cm 3 / g, 0.0017cm 3 / g, 0.0015cm 3 / g, 0.0013cm 3 / g, 0.0010cm 3 / g, 0.0008cm 3 / g, 0.0005cm 3 / g, 0.0003cm 3 / g.

[0066] In this embodiment of the application, the specific surface area S1 of the negative electrode material 100, measured by carbon dioxide adsorption-desorption, is greater than 100 m². 2 / g. Carbon dioxide adsorption-desorption primarily measures the specific surface area of ​​ultrapores. This application controls the specific surface area S1, measured by carbon dioxide adsorption-desorption, to be greater than 100 m². 2 / g is beneficial for providing more sodium deposition sites, thereby increasing the capacity of the negative electrode material 100. In some embodiments of this application, the specific surface area S1 of the negative electrode material 100, as measured by carbon dioxide adsorption-desorption, is greater than 200m². 2 / g. In some embodiments of this application, the specific surface area S1 of the negative electrode material 100, measured by carbon dioxide adsorption-desorption, is greater than 300m². 2 / g. In some embodiments of this application, the specific surface area S1 of the negative electrode material 100, measured by carbon dioxide adsorption-desorption, is greater than 400m². 2 / g. For example, the specific surface area S1 of the negative electrode material 100, measured by carbon dioxide adsorption-desorption, is 110 m². 2 / g, 150m 2 / g、200m 2 / g、250m 2 / g、300m 2 / g, 350m 2 / g、400m 2 / g.

[0067] In this embodiment, the ratio of the specific surface area S1 measured by carbon dioxide adsorption-desorption to the specific surface area S2 measured by nitrogen adsorption-desorption of the negative electrode material 100, S1 / S2, is greater than 30. Controlling the ratio S1 / S2 to S1 is greater than 30 allows for more sodium deposition sites provided by the micropores, which is beneficial for improving the capacity of the negative electrode material 100. In some embodiments of this application, the ratio S1 / S2 of the specific surface area S1 measured by carbon dioxide adsorption-desorption to S2 measured by nitrogen adsorption-desorption of the negative electrode material 100 is greater than 50. In some embodiments of this application, the ratio S1 / S2 of the specific surface area S1 measured by carbon dioxide adsorption-desorption to S2 measured by nitrogen adsorption-desorption of the negative electrode material 100 is greater than 70. For example, the ratio S1 / S2 of the specific surface area S1 of the negative electrode material 100 measured by carbon dioxide adsorption-desorption to the specific surface area S2 measured by nitrogen adsorption-desorption is 31, 40, 50, 60, 70, 80, 90, or 100.

[0068] In this embodiment, the negative electrode material 100 has a core-shell structure in which a soft carbon coating layer 102 coats a hard carbon 101. Hard carbon is a carbon material that is difficult to graphitize even at temperatures above 3000°C, and its structure is relatively disordered. Soft carbon is an amorphous material that can be graphitized at 2800°C, and its structure is relatively ordered with a high degree of graphitization, typically exhibiting a graphite microcrystal arrangement and carbon layer spacing similar to graphite. The coating layer 102 can completely or partially cover the surface of the hard carbon 101. Completely covering the surface of the hard carbon 101 with the coating layer 102 is beneficial for improving the initial coulombic efficiency and compaction density of the negative electrode material 100.

[0069] In this embodiment, the thickness of the coating layer 102 is 1 nm to 10 nm. A thinner coating layer 102 facilitates ion diffusion and transport, improving the kinetic performance of the negative electrode material 100. In some embodiments of this application, the thickness of the coating layer 102 is 1 nm to 5 nm. Exemplarily, the thickness of the coating layer 102 can be 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, or 10 nm.

[0070] In this embodiment, the intensity ratio of the D peak to the G peak in the Raman spectrum of the negative electrode material 100 is ID / IG ≥ 1.10. ID / IG is the ratio of the peak intensities of the D peak to the G peak calculated from the Raman spectrum. Raman spectroscopy can measure information about the surface of the particles of the negative electrode material 100. The more material defects there are, the more prominent and intense the D peak is, and the larger the ID / IG ratio is. A larger ID / IG ratio indicates that there are more defects in the coating layer 102, which can increase the wettability of the negative electrode material 100 in the electrolyte and improve the kinetic performance of the negative electrode material 100.

[0071] In some embodiments of this application, the intensity ratio of the D peak to the G peak in the Raman spectrum of the negative electrode material 100, ID / IG, is 1.12 ≤ ID / IG ≤ 1.3. A suitable ID / IG ratio allows the negative electrode material 100 to achieve increased wettability while avoiding an increase in side reactions caused by excessive defects. For example, the intensity ratio of the D peak to the G peak in the Raman spectrum of the negative electrode material 100, ID / IG, can be 1.12, 1.13, 1.14, 1.15, 1.16, 1.17, 1.18, 1.19, 1.2, 1.22, 1.24, 1.25, 1.26, 1.28, or 1.3.

[0072] In this embodiment, the carbon interlayer spacing d002 of the negative electrode material 100 is 0.370 nm ≤ d002 ≤ 0.380 nm. The interlayer spacing d002 is the interlayer spacing of the carbon material calculated from the (002) peak of the XRD (X-ray diffraction) spectrum. A larger interlayer spacing in the negative electrode material 100 is beneficial for ion insertion and extraction, and helps improve the kinetic performance of the negative electrode material 100. For example, the carbon interlayer spacing d002 of the negative electrode material 100 is 0.370 nm, 0.372 nm, 0.375 nm, 0.378 nm, and 0.380 nm.

[0073] In this embodiment, the full width at half maximum (FWHM) of the XRD diffraction peak of the (002) crystal plane of the negative electrode material 100 is less than 7.0°. That is, in the XRD pattern of the negative electrode material 100, the FWHM of the (002) peak (i.e., the peak width at 1 / 2 height) is less than 7.0°. A narrower FWHM for the (002) peak in the negative electrode material 100 results in a larger crystal domain size, which is beneficial for improving the compaction density of the negative electrode material 100. In some embodiments, the FWHM of the XRD diffraction peak of the (002) crystal plane of the negative electrode material 100 is less than 6.8°. In some embodiments, the FWHM of the XRD diffraction peak of the (002) crystal plane of the negative electrode material 100 is less than 6.6°.

[0074] In this embodiment, the full width at half maximum (FWHM) of the XRD diffraction peak of the (100) crystal plane of the negative electrode material 100 is less than 3.5°. That is, in the XRD pattern of the negative electrode material 100, the FWHM of the (100) peak (i.e., the peak width at 1 / 2 height) is less than 3.5°. A narrower FWHM of the (100) peak in the negative electrode material 100 results in a larger crystal domain size, which is beneficial for improving the compaction density of the negative electrode material 100. In some embodiments, the FWHM of the XRD diffraction peak of the (100) crystal plane of the negative electrode material 100 is less than 3.4°. In some embodiments, the FWHM of the XRD diffraction peak of the (100) crystal plane of the negative electrode material 100 is less than 3.2°.

[0075] In this embodiment, the D50 particle size of the negative electrode material 100 is 3μm-15μm. Exemplarily, the D50 particle size of the negative electrode material 100 is 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, or 15μm. A suitable D50 particle size for the negative electrode material 100 is beneficial for improving its volumetric energy density, for dispersion in the negative electrode slurry, and for the coating process during electrode fabrication. D50 (Dv50) is the particle size value at which the cumulative distribution percentage reaches 50%, also known as the median diameter or median particle size. The D50 particle size of the negative electrode material 100 can be obtained by testing with a laser particle size analyzer.

[0076] In this embodiment, the powder compaction density of the negative electrode material 100 is greater than 1.03 g / cm³. 3 Powder compaction density refers to the density of a powder material after compression under a certain pressure. In some embodiments of this application, the powder compaction density of the negative electrode material 100 under a pressure of 5T (tons) is greater than or equal to 1.04 g / cm³. 3 In some embodiments of this application, the compacted density of the negative electrode material 100 powder under a pressure of 5T (tons) is greater than or equal to 1.05 g / cm³. 3 In some embodiments of this application, the compacted density of the negative electrode material 100 powder under a pressure of 5T (tons) is greater than or equal to 1.06 g / cm³. 3 The negative electrode material 100 has a relatively high compaction density, which is beneficial for achieving high battery capacity. The powder compaction density can be measured using a powder compaction density meter.

[0077] In some embodiments of this application, the reversible specific capacity of the negative electrode material 100 is greater than 340 mAh / g. Reversible specific capacity refers to the amount of electricity that a battery can reversibly release and store during charging and discharging. A larger reversible specific capacity means that the battery can store and release more energy during charging and discharging, thereby increasing the battery's energy density. A larger reversible specific capacity also means that the battery can undergo more charge-discharge cycles under the same usage conditions, thus extending the battery's lifespan, reducing charging frequency, and improving user experience. In some embodiments of this application, the reversible specific capacity of the negative electrode material 100 is greater than or equal to 345 mAh / g. In some embodiments of this application, the reversible specific capacity of the negative electrode material 100 is greater than 350 mAh / g. In some embodiments of this application, the reversible specific capacity of the negative electrode material 100 is greater than 360 mAh / g.

[0078] In this embodiment, the initial coulombic efficiency of the negative electrode material 100 is greater than or equal to 88%. Initial coulombic efficiency is the efficiency with which a battery can effectively store and release charge during its first charge and discharge cycle. Initial coulombic efficiency = (initial discharge capacity / initial charge capacity) × 100%. A higher initial coulombic efficiency in the negative electrode material 100 results in lower initial losses, which is beneficial for improving the overall performance and range of the battery. Exemplarily, the initial coulombic efficiency of the negative electrode material 100 can be 88%, 88.2%, 88.3%, 88.5%, 88.6%, 88.8%, 89%, or 89.3%.

[0079] The negative electrode material 100 of this application embodiment, by coating the surface of the hard carbon core with a soft carbon coating layer and controlling it to have a high total pore volume, a high proportion of ultra-micropores and a low specific surface area, can make the negative electrode material 100 have a high capacity, a high initial coulombic efficiency and a high compaction density.

[0080] The negative electrode material 100 provided in this application embodiment can be applied to sodium-ion batteries or lithium-ion batteries, and then applied to systems or scenarios that use sodium-ion batteries or lithium-ion batteries, such as electronic devices, energy storage power stations, industrial and commercial energy storage, residential energy storage, base station backup power, data center backup power, etc.

[0081] Conventional activation and pore-forming methods struggle to control the pore size of most pores to a small micropore size, easily resulting in a large number of ineffective pores (macropores, mesopores, and some micropores) that contribute little to the actual capacity. This leads to low utilization of the sodium storage space in the anode material. While this can improve the capacity of the anode material to some extent, the compaction density also decreases significantly, ultimately resulting in a negligible increase in energy density. Therefore, this application provides a method for preparing an anode material with a rich microporous structure, achieving both high capacity and high compaction density.

[0082] The method for preparing the negative electrode material provided in this application includes:

[0083] S101. The first carbon source is pretreated by heating to obtain a pretreated product;

[0084] S102. The pretreated product obtained in step S101 is mixed with a zinc-containing catalyst, and then activated in a nitrogen atmosphere for the first stage, and then activated in a carbon dioxide atmosphere for the second stage to obtain the activated product.

[0085] S103. The activated product obtained in step S102 is subjected to a first carbonization treatment to obtain hard carbon.

[0086] S104. The hard carbon obtained in step S103 is mixed with the second carbon source and then subjected to a second carbonization treatment to form a coating layer on the surface of the hard carbon, thereby obtaining a negative electrode material.

[0087] The method for preparing the anode material provided in this application utilizes a special physicochemical activation process to induce the directional activation of carbon dioxide (CO2) through the catalytic effect of zinc, thereby preparing a carbon anode material rich in ultra-microporous structure. This method achieves high compaction density and high first-time coulombic efficiency while improving capacity. Furthermore, by using a liquid-phase carbon coating process, the interface is improved while further filling the ineffective pores on the hard carbon surface, thus enhancing compaction density and first-time coulombic efficiency.

[0088] In step S101, the first carbon source can be one or more of asphalt, resin, and biomass. Asphalt can be petroleum asphalt, coal tar, etc. Resin can be, for example, phenolic resin. Biomass can be, for example, nutshells, etc.

[0089] The heating pretreatment can cause some small molecules to overflow and undergo pre-crosslinking, improving the quality of the negative electrode material precursor, resulting in higher carbonization uniformity and better structural integrity. In this embodiment, the heating pretreatment can be carried out in a protective atmosphere, such as a nitrogen atmosphere. The nitrogen flow rate can be 0.5L / min-10L / min, for example, 0.5L / min, 1L / min, 2L / min, 3L / min, 4L / min, 5L / min, 6L / min, 7L / min, 8L / min, 9L / min, or 10L / min.

[0090] In this embodiment, the temperature of the heating pretreatment can be 200℃-600℃. A suitable heating pretreatment temperature allows the small molecules and heteroatom groups of the first carbon source to slowly decompose and overflow, avoiding the formation of macropores. Simultaneously, after the heteroatoms overflow, the carbon structure crosslinks and rearranges to form a bridging network structure, ultimately resulting in more micropores. Exemplarily, the heating pretreatment temperature can be 200℃, 250℃, 300℃, 350℃, 400℃, 450℃, 500℃, 550℃, or 600℃. The heating rate of the heating pretreatment can be 1℃ / min-6℃ / min, and the holding time can be 2-5 hours; exemplaryly, the heating rate of the heating pretreatment can be 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, or 6℃ / min, and the holding time can be 2 hours, 3 hours, 4 hours, or 5 hours.

[0091] In some implementations, when the first carbon source includes biomass, it can be pretreated directly by heating in a nitrogen atmosphere.

[0092] In other embodiments, when the first carbon source includes one or more of pitch and resin, the heat pretreatment of the first carbon source can be performed by mixing the first carbon source with a crosslinking agent and then performing heat pretreatment. Introducing the crosslinking agent during the heat pretreatment process can enable the first carbon source to form a pre-crosslinked oxidation product, whose crosslinking sites can provide pore-forming sites, which is beneficial for the subsequent formation of narrow pores with more uniform size and distribution.

[0093] In this embodiment, the crosslinking agent may include anhydride-based crosslinking agents. The presence of anhydride groups in the anhydride-based crosslinking agent allows the first carbon source to be pre-crosslinked smoothly. Specifically, the anhydride-based crosslinking agent may include one or more of 1,2,4-phenyltriglyceridyl anhydride, maleic anhydride, and maleic anhydride. These crosslinking agents have small molecular weights, which is beneficial for the subsequent formation of narrow ultramicropores in the negative electrode material. In some embodiments, only 1,2,4-phenyltriglyceridyl anhydride is used as the crosslinking agent; in some embodiments, only maleic anhydride is used as the crosslinking agent. The mass ratio of the first carbon source to the crosslinking agent may be 1:(0.1-0.5). For example, the mass ratio of the first carbon source to the crosslinking agent may be 1:0.1, 1:0.15, 1:0.2, 1:0.3, 1:0.4, or 1:0.5.

[0094] In this embodiment, the particle size of the pretreated product can be controlled within the range of 3 μm to 15 μm. A suitable particle size of the pretreated product can ultimately yield a negative electrode material with a suitable particle size, enabling the negative electrode material to possess both good kinetic performance and high first-efficiency. For example, the particle size of the pretreated product can be controlled within the range of 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, and 15 μm.

[0095] In step S102, the zinc-containing catalyst can be one or more inorganic zinc-containing compounds, including zinc salts and zinc oxides. The zinc salt can be zinc acetate, zinc carbonate, zinc oxalate, etc., and the zinc oxide can be zinc oxide (ZnO). The zinc-containing catalyst can induce the directional activation of the pretreated product by carbon dioxide, thereby achieving the formation of abundant ultrapores. The directional activation can be achieved by CO2 etching the pretreated product to form micropores under the catalysis of the zinc-containing catalyst, with the CO2 activation reaction occurring directionally towards the interior of the pretreated product as the zinc-containing catalyst is distributed. The mass ratio of the pretreated product to the zinc-containing catalyst can be 1:(0.1-3). For example, the mass ratio of the pretreated product to the zinc-containing catalyst can be 1:0.1, 1:0.2, 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, or 1:3.

[0096] In this embodiment, the first stage of activation is carried out under a nitrogen atmosphere, and the nitrogen flow rate can be 0.1 L / min to 0.5 L / min, specifically, for example, 0.1 L / min, 0.2 L / min, 0.3 L / min, 0.4 L / min, or 0.5 L / min. A suitable nitrogen flow rate is beneficial for more uniform pre-activation.

[0097] In this embodiment, the activation temperature for the first stage can be 200℃-300℃. After mixing the pretreated product with the zinc-containing catalyst, it is first treated at a suitable low temperature under a nitrogen atmosphere. This softens the first carbon source and allows the zinc-containing catalyst to fully penetrate and disperse into the bulk phase of the first carbon source, thus completing the pre-activation. Specific activation temperatures for the first stage can be, for example, 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, 260℃, 270℃, 280℃, 290℃, or 300℃.

[0098] In this embodiment, the heating rate of the first activation stage can be 1℃ / min-10℃ / min, and the holding time can be 1-2 hours. For example, the heating rate of the first activation stage can be 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, or 10℃ / min, and the holding time can be 1 hour, 1.5 hours, or 2 hours. A suitable heating rate promotes more uniform pre-activation, and a suitable holding time ensures more complete pre-activation.

[0099] In this embodiment, the second-stage activation is carried out under a carbon dioxide atmosphere. The carbon dioxide flow rate can be 0.1 L / min to 2 L / min, specifically, for example, 0.1 L / min, 0.2 L / min, 0.3 L / min, 0.4 L / min, 0.5 L / min, 0.6 L / min, 0.8 L / min, 1 L / min, 1.2 L / min, 1.5 L / min, 1.8 L / min, or 2 L / min. Appropriate control of the carbon dioxide flow rate is beneficial for utilizing carbon dioxide to activate the pretreated product, ensuring activation efficiency, and avoiding excessively rapid reaction and pore size expansion, ultimately contributing to the formation of a narrow pore structure.

[0100] In this embodiment, the activation temperature of the second stage can be 800℃-950℃, specifically, for example, 800℃, 820℃, 850℃, 870℃, 890℃, 900℃, 920℃, 930℃, or 950℃. Controlling the second stage activation at a relatively higher suitable temperature allows the zinc-containing catalyst to better induce the carbon dioxide activation pretreatment product and controls the reaction rate to form more micropores.

[0101] In this embodiment, the heating rate of the second-stage activation can be 1℃ / min-10℃ / min, and the holding time can be 2-6 hours. For example, the heating rate of the second-stage activation can be 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, or 10℃ / min, and the holding time can be 2 hours, 3 hours, 4 hours, 5 hours, or 6 hours. A suitable heating rate promotes more uniform activation, and a suitable holding time allows for better control of the activation degree and pore size distribution.

[0102] In step S103, the temperature of the first carbonization treatment is 1200℃-1400℃. The heating rate of the first carbonization treatment can be 1℃ / min-6℃ / min, and the holding time can be 2-4 hours. Suitable first carbonization treatment temperature, heating rate, and holding time allow the activated product to further crosslink uniformly, stabilizing the structure and ensuring complete carbonization. Simultaneously, a suitable first carbonization treatment temperature allows the obtained hard carbon to retain more ion diffusion channels, improving kinetic performance. For example, the temperature of the first carbonization treatment can be 1200℃, 1250℃, 1300℃, 1350℃, or 1400℃. The heating rate of the first carbonization treatment can be 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, or 6℃ / min, and the holding time can be 2 hours, 3 hours, or 4 hours.

[0103] In step S104, the coating process for the coating layer is a liquid-phase coating process, and the second carbon source can be a carbon source material with a softening point of less than 200°C. For example, the second carbon source can be asphalt. The second carbon source can be added at a coating amount of 0.5%-2.5%, where the coating amount is based on the residual carbon value. For example, the second carbon source can be added at coating amounts of 0.5%, 1.0%, 1.5%, 2.0%, and 2.5%.

[0104] In this embodiment, the temperature of the second carbonization treatment can be 900℃-1200℃. The heating rate can be 1℃ / min-10℃ / min, and the holding time can be 1-4 hours. Suitable second carbonization treatment temperature, heating rate, and holding time can form a complete and thin high-quality coating layer. For example, the temperature of the second carbonization treatment can be 900℃, 950℃, 1000℃, 1050℃, 1100℃, 1150℃, or 1200℃. The heating rate of the first carbonization treatment can be 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, or 10℃ / min, and the holding time can be 1 hour, 2 hours, 3 hours, or 4 hours.

[0105] The method for preparing the negative electrode material provided in this application, through a special physicochemical activation process and liquid phase coating process, enables the product to have a higher ultra-micropore volume and proportion, improves the utilization rate of the pore structure for sodium storage, and thus obtains a higher sodium storage capacity and a relatively higher compaction density; at the same time, it can also make the negative electrode material have a smaller (002) peak and (100) peak half width at half maximum, further improving the compaction density and increasing the capacity.

[0106] This application also provides a composite negative electrode material, which includes the negative electrode material 100 described in the embodiments of this application or the negative electrode material 100 prepared by the preparation method described in the embodiments of this application, and includes a second negative electrode active material different from the negative electrode material 100. The second negative electrode active material and the negative electrode material 100 can be in an attachment-attached, coating-coated, or mutually bonded relationship. The second negative electrode active material can be various negative electrode active materials capable of sodium ion intercalation / deintercalation that can be used as a negative electrode, such as natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), graphene, carbon nanotubes, conductive polymers, etc.

[0107] See Figure 2 , Figure 2 This is a cross-sectional structural diagram of the negative electrode sheet 20 provided in this application embodiment. The negative electrode sheet 20 includes a negative electrode current collector 21 and a negative electrode active layer 22 located on the negative electrode current collector 21. The negative electrode active layer 22 includes a negative electrode active material 221, which includes the negative electrode material 100 or composite negative electrode material described in this application embodiment. In some embodiments, the negative electrode active material 221 may be entirely composed of the aforementioned negative electrode material 100 and / or the aforementioned composite negative electrode material. In other embodiments, the negative electrode active material 221 may also include the aforementioned negative electrode material 100 and / or the aforementioned composite negative electrode material, and may also include other carbon materials, such as one or more of natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, and porous carbon materials.

[0108] In this embodiment, the mass percentage of the negative electrode active material 221 in the negative electrode active layer 22 can be greater than or equal to 92%. In some embodiments, the mass percentage of the negative electrode active material 221 in the negative electrode active layer 22 can be, for example, 92%, 93%, 94%, 95%, 96%, or 97%.

[0109] In this embodiment, the negative electrode current collector 21 can be a metal foil, such as copper foil, aluminum foil, gold foil, platinum foil, etc.

[0110] In this embodiment, the negative electrode active layer 22 may further include a certain amount of binder, conductive agent, and other components. The binder may be, for example, sodium carboxymethyl cellulose (CMC-Na), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (NaPAA), etc. The conductive agent may be, for example, amorphous carbon, carbon nanotubes, carbon fibers, graphene, etc. The above-mentioned binders and conductive agents are merely illustrative examples and are not limited thereto.

[0111] See Figure 3 This application also provides a battery, specifically a sodium-ion battery 300. The sodium-ion battery 300 includes a positive electrode 10, a negative electrode 20, a separator 30, an electrolyte 40, and corresponding connecting accessories and circuits. The positive electrode 10 includes a positive active material 121, and the negative electrode 20 includes a negative active material 221, which in turn includes a negative material 100. The separator 30 is disposed between the positive electrode 10 and the negative electrode 20, and the electrolyte 40 fills the space between the positive electrode 10 and the negative electrode 20 and wets the separator 30. The electrolyte 40 serves as a carrier for sodium ions to transport between the positive and negative electrodes, and the separator 30 allows sodium ions to pass through while separating the positive and negative electrodes to prevent short circuits. During charging, sodium ions are released from the positive electrode active material 121 of the positive electrode 10, pass through the electrolyte 40, and then intercalate into the negative electrode active material 221 of the negative electrode 20. During discharging, sodium ions are released from the negative electrode active material 221, pass through the electrolyte 40, and then insert into the positive electrode active material 121. The sodium-ion battery of this embodiment, by employing the negative electrode material 100 of this application, can maintain a high capacity while reducing the risk of sodium deposition, effectively improving the cycle performance and safety performance of the sodium-ion battery.

[0112] In this embodiment, the positive electrode 10 includes a positive current collector 11 and a positive active layer 12 located on the positive current collector 11. The positive active layer 12 includes a positive active material 121, which can be one or more of various available sodium-ion battery positive active materials, such as layered sodium transition metal oxides, Prussian blue (white) compounds, and sodium polyanionic compounds. In this embodiment, the layered sodium transition metal oxide can be, for example, sodium nickel iron manganese (NaNi). 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 (abbreviated as NFM), Prussian blue (white) compounds such as Prussian white (Na2Mn[Fe(CN)6], abbreviated as PBA), and sodium polyanionic compounds such as sodium iron phosphate (NaFePO4, abbreviated as NFP). The mass percentage of the positive electrode active material 121 in the positive electrode active layer 12 can be greater than or equal to 92%. In some embodiments, the mass percentage of the positive electrode active material 121 in the positive electrode active layer 12 can be, for example, 92%, 93%, 94%, 95%, 96%, or 97%.

[0113] The positive current collector 11 can be a metal foil, such as aluminum foil, gold foil, platinum foil, etc.

[0114] In the sodium-ion battery 300, the electrolyte 40 serves as the transport medium for sodium ions during transport between the positive electrode 10 and the negative electrode 20. In this embodiment, the electrolyte 40 comprises an organic solvent, an electrolyte salt, and additives, wherein both the electrolyte salt and the additives are dissolved in the organic solvent.

[0115] In the embodiments of this application, the organic solvents include, but are not limited to, one or more of carbonate solvents, ether solvents, and carboxylic acid ester solvents. Specifically, carbonate solvents include, but are not limited to, one or more of dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, trifluoromethyl ethylene carbonate, bis(2,2,2-trifluoroethyl) carbonate, and (2,2,2-trifluoroethyl)methyl carbonate. Ether solvents include, but are not limited to, one or more of tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, dimethoxymethane, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and bis(2,2,2-trifluoroethyl) ether. Carboxylic acid ester solvents include, but are not limited to, one or more of methyl formate, ethyl formate, ethyl acetate, propyl acetate, propyl propionate, methyl difluoroacetate, and methyl trifluoroacetate.

[0116] In the embodiments of this application, the electrolyte salts include, but are not limited to, NaClO4, NaBF4, NaPF6, NaAsF6, NaCF3SO3, NaTDI, Na[(CF3SO2)2N], Na[(FSO2)2N], and Na[(C m F 2m+1 SO2)(C n F 2n+1 One or more of SO2 and N are included, where m and n are natural numbers. In some embodiments of this application, the molar concentration of the electrolyte salt in the electrolyte solution can be 0.01 mol / L to 5.0 mol / L. In some embodiments, the molar concentration of the electrolyte salt in the electrolyte solution can be, for example, 0.01 mol / L, 0.1 mol / L, 0.5 mol / L, 0.8 mol / L, 1.0 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, 2.0 mol / L, 3.0 mol / L, 4.0 mol / L, or 5.0 mol / L.

[0117] In this application, the additives may include, but are not limited to, positive electrode film-forming additives, negative electrode film-forming additives, flame retardants, etc. In some embodiments, the additives may be one or more of the following: fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), succinic anionyl nitrile (SN), glutaronitrile, adiponitrile, 1,2-bis(2-cyanoethoxy)ethane (DENE), 1,3,6-hexanetrionitrile (HTCN), sodium bis(oxalato)borate (NaBOB), sodium difluorooxalatoborate (NaDFOB), sodium difluorobis(oxalato)phosphate (NaDFOP), and sodium difluorophosphate (NaPO2F2). The total mass content of the additives may be less than 10%, for example, 9%, 7%, 5%, 3%, 2%, 1%, or 0.5%.

[0118] In this embodiment, the separator 30 is located between the positive electrode 10 and the negative electrode 20, and is used to block the passage of electrons while allowing sodium ions to pass through. The separator 30 includes, but is not limited to, single-layer polypropylene (PP), single-layer polyethylene (PE), double-layer PP / PE, double-layer PP / PP, triple-layer PP / PE / PP, and ceramic-coated PE.

[0119] The specific shape or type of the sodium-ion battery in this application embodiment is not limited. It can be a square battery, a button battery, a cylindrical battery, a pouch battery, etc.; it can be a wound battery or a stacked battery.

[0120] The identification of negative electrode materials in batteries, cells, or battery packs can be carried out in the following manner: disassemble the battery, cell, or battery pack, scrape off the negative electrode material from the negative electrode sheet, re-disperse it ultrasonically with N-methylpyrrolidone (NMP) solvent, separate the negative electrode material by centrifugation, and after multiple ultrasonic washing and centrifugation, the conductive agent and negative electrode material are basically separated to obtain the negative electrode material to be tested. Perform various necessary tests on the negative electrode material to obtain the above-mentioned characteristic parameters of the negative electrode material.

[0121] The sodium-ion battery provided in this application embodiment can be used as a single cell battery, energy storage battery, power battery, etc. It can be used in mobile phones, tablets, power banks, portable computers, laptops and other wearable or portable electronic devices, as well as in vehicles, energy storage devices, base stations, energy storage systems and other equipment products to enhance product competitiveness.

[0122] See Figure 4 This application also provides an electrical device 400, which includes a power module 401 and the sodium-ion battery 300 described above in this application embodiment. The battery supplies power to the power module 401. The electrical device using the sodium-ion battery of this application embodiment has high stability.

[0123] In this application embodiment, the electrical equipment 400 can be various devices that rely on electrical energy conversion for operation in daily life and industrial production, such as electronic devices, vehicles, ships, aerospace equipment, energy storage systems, drones, power stations, communication equipment, and communication base stations. Among them, electronic devices can be consumer electronics products, such as mobile phones, tablets, desktop computers, laptops, power banks, portable computers, smart screens, displays, audio equipment, in-vehicle products, and other wearable or portable electronic devices (such as glasses, watches, bracelets, and headphones). Vehicles can be various electric vehicles such as electric cars, electric bicycles, and electric trains. Using the battery provided in this application embodiment can improve the performance of electrical equipment and enhance product competitiveness.

[0124] This application also provides an energy storage device, which includes a battery module. The battery module includes a battery mounting portion and the aforementioned battery mounted on the battery mounting portion. The energy storage device may include one or more battery modules, and each battery module includes one or more of the aforementioned batteries. The energy storage device may also include a battery management system electrically connected to the battery modules. The battery management system is used to monitor or control the state of each battery in each battery module, preventing overcharging and over-discharging of the batteries and extending their service life.

[0125] This application embodiment also provides an energy storage system, including the above-mentioned energy storage device and a power converter electrically connected. The power converter is used to perform power conversion processing on voltage and / or current, and input the changed voltage and / or current to the energy storage device.

[0126] The technical solution of this application will be further described below with reference to several embodiments.

[0127] Example 1

[0128] A method for preparing a negative electrode material includes the following steps:

[0129] S101. Using petroleum asphalt with a softening point of 280℃ as raw material, the particle size is controlled between 5μm and 6μm. Petroleum asphalt and 1,2,4-benzenetricarboxylic anhydride are mixed evenly at a mass ratio of 1:0.1. Nitrogen gas is introduced and heated for pre-crosslinking oxidation treatment to obtain the pretreated product. The nitrogen flow rate is 1L / min, the heating rate is 5℃ / min, the holding temperature is 400℃, and the holding time is 4h.

[0130] S102. The pretreated product and zinc acetate are uniformly physically mixed at a mass ratio of 1:0.5. The mixture is first activated in a nitrogen atmosphere and then activated in a carbon dioxide atmosphere to obtain the activated product. The first activation process is carried out with nitrogen gas at a flow rate of 0.2 L / min, at a temperature of 240℃, a heating rate of 10℃ / min, and a holding time of 2 h. The second activation process is carried out with CO2 gas at a flow rate of 0.5 L / min, at a temperature of 900℃, a heating rate of 3℃ / min, and a holding time of 4 h.

[0131] S103. The activated product is subjected to a first carbonization treatment to obtain hard carbon. The first carbonization temperature is 1200℃, the heating rate is 5℃ / min, and the holding time is 2h.

[0132] S104. After physically mixing the hard carbon and coated asphalt at a coating amount of 1.5% (based on the residual carbon value), a second carbonization treatment is carried out. The second carbonization temperature is 1000℃, the heating rate is 10℃ / min, the holding time is 2h, and the negative electrode material is obtained after cooling.

[0133] Figure 5 This is an HRTEM (High Resolution Transmission Electron Microscope) image of the negative electrode material prepared in Example 1 of this application. Figure 5 It can be seen that the obtained negative electrode material includes hard carbon 101 and a coating layer 102 formed on the surface of hard carbon 101, and the thickness of the coating layer 102 is about 2.2 nm.

[0134] Example 2

[0135] A method for preparing a negative electrode material includes the following steps:

[0136] S101. Using coal tar pitch with a softening point of 250℃ as raw material, the particle size is controlled between 6μm and 8μm. Coal tar pitch and maleic anhydride are mixed evenly at a mass ratio of 1:0.15. Nitrogen gas is introduced and heated for pre-crosslinking oxidation treatment to obtain the pretreated product. The nitrogen flow rate is 2L / min, the heating rate is 1℃ / min, the holding temperature is 600℃, and the holding time is 2h.

[0137] S102. The pretreated product and zinc carbonate are uniformly physically mixed at a mass ratio of 1:1. The mixture is first activated in a nitrogen atmosphere and then activated in a carbon dioxide atmosphere to obtain the activated product. The first activation process is carried out with nitrogen gas at a flow rate of 0.2 L / min, at a temperature of 200℃, a heating rate of 5℃ / min, and a holding time of 1 h. The second activation process is carried out with CO2 gas at a flow rate of 0.5 L / min, at a temperature of 900℃, a heating rate of 2℃ / min, and a holding time of 6 h.

[0138] S103 and S104 are the same as in Example 1.

[0139] Example 3

[0140] A method for preparing a negative electrode material includes the following steps:

[0141] S101. Using a mixture of petroleum asphalt with a softening point of 200℃ and phenolic resin (mass ratio of asphalt to phenolic resin = 8:2) as raw material, the mixture and 1,2,4-benzenetricarboxylic anhydride are mixed evenly at a mass ratio of 1:0.1. Nitrogen gas is introduced and heated for pre-crosslinking oxidation treatment to obtain a pretreated product. The nitrogen flow rate is 1L / min, the heating rate is 5℃ / min, the holding temperature is 250℃, and the holding time is 4h.

[0142] S102. The pretreated product and zinc oxalate are uniformly physically mixed at a mass ratio of 1:3. The mixture is first activated in a nitrogen atmosphere and then activated in a carbon dioxide atmosphere to obtain the activated product. The first activation process is carried out with nitrogen gas at a flow rate of 0.2 L / min, at a temperature of 300℃, a heating rate of 10℃ / min, and a holding time of 2 h. The second activation process is carried out with CO2 gas at a flow rate of 0.5 L / min, at a temperature of 800℃, a heating rate of 3℃ / min, and a holding time of 4 h.

[0143] S103. The activated product is subjected to a first carbonization treatment to obtain hard carbon. The first carbonization temperature is 1300℃, the heating rate is 2℃ / min, and the holding time is 4h.

[0144] S104. After physically mixing the hard carbon and coated asphalt at a coating amount of 0.5% (based on the residual carbon value), a second carbonization treatment is carried out. The second carbonization temperature is 900℃, the heating rate is 10℃ / min, the holding time is 2h, and the negative electrode material is obtained after cooling.

[0145] Example 4

[0146] A method for preparing a negative electrode material includes the following steps:

[0147] S101. Using coconut shells as raw material, nitrogen gas is introduced for heating pretreatment, followed by pulverization to obtain the pretreated product. The nitrogen flow rate is 1L / min, the heating rate is 5℃ / min, the holding temperature is 500℃, the holding time is 4h, and the material is pulverized to 4μm-6μm.

[0148] S102. The pretreated product and zinc acetate are uniformly physically mixed at a mass ratio of 1:0.5. The mixture is first activated in a nitrogen atmosphere and then activated in a carbon dioxide atmosphere to obtain the activated product. The first activation process is carried out with nitrogen gas at a flow rate of 0.2 L / min, the temperature is 200℃, the heating rate is 2℃ / min, and the holding time is 2h. The second activation process is carried out with CO2 gas at a flow rate of 0.5 L / min, the temperature is 950℃, the heating rate is 3℃ / min, and the holding time is 2h.

[0149] S103. The activated product is subjected to a first carbonization treatment to obtain hard carbon. The first carbonization temperature is 1400℃, the heating rate is 5℃ / min, and the holding time is 2h.

[0150] S104. After physically mixing the hard carbon and coated asphalt at a coating amount of 2.5% (based on the residual carbon value), a second carbonization treatment is carried out. The second carbonization temperature is 1200℃, the heating rate is 5℃ / min, the holding time is 2h, and the negative electrode material is obtained after cooling.

[0151] Comparative Example 1

[0152] A method for preparing a negative electrode material includes the following steps:

[0153] S101. Using petroleum asphalt with a softening point of 280℃ as raw material, the particle size is controlled at 5-6 μm. The asphalt and 1,2,4-benzenetricarboxylic anhydride are mixed evenly at a mass ratio of 1:0.1 and then subjected to pre-crosslinking oxidation treatment. The nitrogen flow rate is 1 L / min, the heating rate is 5℃ / min, the holding temperature is 400℃, and the holding time is 4h.

[0154] S102. The pre-crosslinked oxidized asphalt is subjected to carbonization treatment at a temperature of 1200℃, a heating rate of 10℃ / min, and a holding time of 2h. After cooling, the asphalt-based hard carbon material can be obtained.

[0155] Comparative Example 2

[0156] The difference from Example 1 is that the coating of S104 is not performed, while the other steps are the same as in Example 1.

[0157] Comparative Example 3

[0158] The difference from Example 1 is that the second stage of activation treatment in step S102, which involves passing carbon dioxide gas, is replaced with passing nitrogen gas; the other steps are the same as in Example 1.

[0159] Comparative Example 4

[0160] The difference from Example 1 is that the activation process in step S102 does not involve the addition of zinc acetate, but only carbon dioxide is used for activation. The other steps are the same as in Example 1.

[0161] The negative electrode materials obtained in Examples 1-4 and Comparative Examples 1-4 were tested as follows, and the results are shown in Table 1:

[0162] 1. The total pore volume V was obtained by performing nitrogen adsorption-desorption tests. 总1 The submicropore volume V1, specific surface area S1, and total pore volume V obtained by carbon dioxide adsorption-desorption testing were also considered. 总2 The submicropore volume V2 and specific surface area S2 are then calculated to obtain S1 / S2 and V1 / V2.

[0163] 2. XRD characterization was used to obtain XRD spectra. The scanning speed was 6° / min, and the scanning range was 10°-60°. The interlayer spacing d002 was calculated based on the (002) peak in the XRD spectrum. The full width at half maximum (FWHM) of the (002) peak and the FWHM of the (100) peak were obtained from the XRD spectrum. Figure 6 This is the XRD (X-ray diffraction) spectrum of the negative electrode material prepared in Example 1 of this application. Figure 6 It can be seen that the negative electrode material obtained in Example 1 has a smaller (002) peak half width at half maximum (FWHM) and a smaller (100) peak half width at half maximum (FWHM).

[0164] 3. Raman spectroscopy characterization was used to obtain Raman spectra, and the peak intensity ratio ID / IG of the D peak and the G peak was calculated based on the Raman spectra.

[0165] 4. The compaction density of the powder under 5T pressure was obtained by using a powder compaction density meter.

[0166] 5. Add the negative electrode material, conductive agent, and binder to deionized water at a mass ratio of 95:4:1, stir and mix thoroughly to obtain a negative electrode slurry, coat the negative electrode slurry onto the copper foil current collector, dry, cold press, and slit to obtain a negative electrode sheet.

[0167] Sodium hexafluorophosphate (NaPF6) was added to propylene carbonate, and then fluoroethylene carbonate was added as an additive at a content of 5 wt% to obtain an electrolyte; the molar concentration of NaPF6 in the electrolyte was 1 mol / L.

[0168] The prepared negative electrode sheet was assembled with a sodium metal electrode and an electrolyte to form a sodium-ion coin cell.

[0169] Charge and discharge test: The assembled button cell was tested on the Blue Electric charge and discharge tester. The discharge was carried out in two steps at 0.1C and 0.01C to 0V respectively, and the charging was carried out at 0.1C to 2.0V to obtain the first reversible specific capacity and the first coulombic efficiency.

[0170] Table 1

[0171]

[0172]

[0173] As shown in Table 1, the anode materials prepared in Examples 1-4 of this application have a high total pore volume, a high proportion of micropores, and a low specific surface area. They also include a hard carbon core and a soft carbon coating layer. The resulting anode materials can simultaneously possess a high first-cycle reversible specific capacity (greater than 340 mAh / g), a high first-cycle coulombic efficiency (greater than 88%), and a high compaction density (greater than 1.03 g / cm³). 3 This allows for higher energy density.

[0174] Comparing Example 1 and Comparative Example 1, it can be seen that Comparative Example 1, due to the lack of activation treatment, has a smaller pore structure in its negative electrode material. Although its compaction density is higher, its specific capacity is only 300.2 mAh / g.

[0175] Comparing Example 1 and Comparative Example 2, it can be seen that Comparative Example 2 has a larger specific surface area S2 due to the lack of coating treatment, resulting in a lower initial efficiency. At the same time, the compaction density and reversible specific capacity are lower than those of Example 1, and more pore structures are not effectively utilized.

[0176] Comparing Example 1 and Comparative Example 3, it can be seen that Comparative Example 3, relying solely on the catalytic activation effect of zinc salt, cannot achieve the ideal activation effect. The proportion of micropores is relatively low, resulting in low reversible specific capacity and compaction density of its anode material product.

[0177] Comparing Example 1 and Comparative Example 4, it can be seen that Comparative Example 4 only uses carbon dioxide for physical activation, which cannot effectively control the pore size, resulting in a lower pore volume of the ultramicropores and less capacity improvement, leading to a lower final reversible specific capacity and a more serious loss of compaction density.

[0178] It should be understood that the use of the terms "first," "second," and various numerical designations in this document is for descriptive convenience only and is not intended to limit the scope of this application.

[0179] In this application, "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone, where A and B can be singular or plural. The character " / " generally indicates that the related objects before and after it are in an "or" relationship.

[0180] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0181] In this application, "-" indicates a range value, including the endpoint values ​​at both ends. For example, the value of a can be 0.5-15, meaning that the value of a can be between 0.5 and 15, and includes the endpoint values ​​of 0.5 and 15.

[0182] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

Claims

1. A negative electrode material, characterized in that, The negative electrode material includes hard carbon and a coating layer disposed on the surface of the hard carbon, the coating layer including soft carbon; The total pore volume of the negative electrode material, measured by carbon dioxide adsorption-desorption, with a pore size of 0.3 nm-1 nm, is greater than 0.03 cm³. 3 / g; the ratio of the ultramicropore volume V1 to the submicropore volume V2 of the negative electrode material is V1 / V2≥20; wherein, the ultramicropore volume V1 is the pore volume with a pore size of 0.3nm-0.7nm measured by carbon dioxide adsorption-desorption; and the submicropore volume V2 is the pore volume with a pore size of 1nm-2nm measured by nitrogen adsorption-desorption; The specific surface area S2 of the negative electrode material, measured by nitrogen adsorption-desorption, is less than 10 m². 2 / g.

2. The negative electrode material as described in claim 1, characterized in that, The specific surface area S2 of the negative electrode material, measured by nitrogen adsorption-desorption, is less than 5 m². 2 / g.

3. The negative electrode material as described in claim 1 or 2, characterized in that, The pore size distribution diagram of the negative electrode material obtained based on carbon dioxide adsorption-desorption characterization shows four peaks in the pore size range of 0.3nm-1nm, and the pore size ranges corresponding to the four peaks are 0.3nm-0.39nm, 0.39nm-0.5nm, 0.5nm-0.7nm, and 0.7nm-1.0nm, respectively.

4. The negative electrode material according to any one of claims 1-3, characterized in that, The total pore volume of the negative electrode material, measured by carbon dioxide adsorption-desorption, with a pore size of 0.3 nm-1 nm, is greater than 0.03 cm³. 3 / g and less than 0.3cm 3 / g; the total pore volume of the negative electrode material, measured by nitrogen adsorption-desorption, with a pore size of 1nm-50nm, is less than or equal to 0.02cm³. 3 / g.

5. The negative electrode material according to any one of claims 1-4, characterized in that, The pore volume of the ultramicropores, V1, is greater than 0.02 cm. 3 / g.

6. The negative electrode material according to any one of claims 1-5, characterized in that, The submicropore volume V2 is less than 0.0025 cm³. 3 / g.

7. The negative electrode material according to any one of claims 1-6, characterized in that, The specific surface area S1 of the negative electrode material, as measured by carbon dioxide adsorption-desorption, is greater than 100 m². 2 / g.

8. The negative electrode material according to any one of claims 1-7, characterized in that, The ratio of the specific surface area S1 measured by carbon dioxide adsorption-desorption to the specific surface area S2 measured by nitrogen adsorption-desorption is S1 / S2 > 30.

9. The negative electrode material according to any one of claims 1-8, characterized in that, The full width at half maximum (FWHM) of the XRD diffraction peak of the (002) crystal plane of the negative electrode material is less than 7.0°.

10. The negative electrode material according to any one of claims 1-9, characterized in that, The full width at half maximum (FWHM) of the XRD diffraction peak of the (100) crystal plane of the negative electrode material is less than 3.5°.

11. The negative electrode material according to any one of claims 1-10, characterized in that, The thickness of the coating layer is 1nm-10nm.

12. The negative electrode material according to any one of claims 1-11, characterized in that, The intensity ratio of the D peak to the G peak in the Raman spectrum of the negative electrode material is ID / IG≥1.

10.

13. The negative electrode material according to any one of claims 1-12, characterized in that, The intensity ratio of the D peak to the G peak in the Raman spectrum of the negative electrode material, ID / IG, is: 1.12≤ID / IG≤1.

3.

14. The negative electrode material according to any one of claims 1-13, characterized in that, The carbon interlayer spacing of the negative electrode material is 0.370nm≤d002≤0.380nm.

15. The negative electrode material according to any one of claims 1-14, characterized in that, The compacted density of the negative electrode material powder is greater than 1.03 g / cm³. 3 The reversible specific capacity of the negative electrode material is greater than 340 mAh / g; the initial coulombic efficiency of the negative electrode material is greater than or equal to 88%.

16. A method for preparing a negative electrode material, characterized in that, include: The first carbon source is pretreated by heating to obtain the pretreated product; The pretreated product was mixed with a zinc-containing catalyst and then activated in a nitrogen atmosphere for the first stage, followed by a carbon dioxide atmosphere for the second stage, to obtain the activated product. The activated product is subjected to a first carbonization treatment to obtain hard carbon. The hard carbon is mixed with a second carbon source and then subjected to a second carbonization treatment to form a coating layer on the surface of the hard carbon, thereby obtaining a negative electrode material.

17. The method for preparing the negative electrode material as described in claim 16, characterized in that, The zinc-containing catalyst includes one or more of zinc salts and zinc oxides.

18. The method for preparing the negative electrode material as described in claim 16 or 17, characterized in that, The nitrogen flow rate for the first stage of activation is 0.1 L / min to 0.5 L / min; the carbon dioxide flow rate for the second stage of activation is 0.1 L / min to 0.5 L / min.

19. The method for preparing the negative electrode material according to any one of claims 16-18, characterized in that, The activation temperature for the first stage is 200℃-300℃; the activation temperature for the second stage is 800℃-950℃.

20. The method for preparing the negative electrode material as described in claim 16, characterized in that, The heating rate for the first stage of activation is 1℃ / min-10℃ / min, and the holding time is 1-2 hours; the heating rate for the second stage of activation is 1℃ / min-10℃ / min, and the holding time is 2-6 hours.

21. The method for preparing the negative electrode material according to any one of claims 16-20, characterized in that, The heating pretreatment is carried out in a nitrogen atmosphere at a temperature of 200℃-600℃.

22. The method for preparing the negative electrode material according to any one of claims 16-21, characterized in that, The first carbon source includes one or more of asphalt, resin, and biomass.

23. The method for preparing the negative electrode material as described in claim 22, characterized in that, The first carbon source includes one or more of asphalt and resin, and the operation of preheating the first carbon source is as follows: the first carbon source is mixed with a crosslinking agent and then preheated.

24. The method for preparing the negative electrode material as described in claim 23, characterized in that, The crosslinking agent includes anhydride crosslinking agents, which include one or more of 1,2,4-benzenetrihydric anhydride, maleic anhydride, and maleic anhydride.

25. The method for preparing the negative electrode material according to any one of claims 16-24, characterized in that, The second carbon source includes carbon source materials with a softening point of less than 200°C.

26. The method for preparing the negative electrode material according to any one of claims 16-25, characterized in that, The temperature of the first carbonization treatment is 1200℃-1400℃; the temperature of the second carbonization treatment is 900℃-1200℃.

27. A composite negative electrode material, characterized in that, The composite anode material includes the anode material according to any one of claims 1-15 or the anode material prepared by the preparation method according to any one of claims 16-26, and a second anode active material different from the anode material.

28. A negative electrode sheet, characterized in that, The negative electrode sheet includes a negative electrode current collector and a negative electrode active layer disposed on the negative electrode current collector. The negative electrode active layer includes the negative electrode material according to any one of claims 1-15; or includes the negative electrode material prepared by the preparation method according to any one of claims 16-26; or includes the composite negative electrode material according to claim 27.

29. A battery, characterized in that, The battery includes a positive electrode, a negative electrode, and an electrolyte disposed between the positive electrode and the negative electrode, wherein the negative electrode includes the negative electrode as described in claim 28.

30. An electrical appliance, characterized in that, The electrical device includes an electrical module and the battery as described in claim 29, wherein the battery supplies power to the electrical module.

31. An energy storage device, characterized in that, The energy storage device includes a battery module, the battery module including a battery mounting section and a battery as described in claim 29, the battery being mounted in the battery mounting section.

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